Experimental Studies On Spontaneous Magnetic Field Produced In The Interaction Of Femtosecond Laser Plasma

Large spontaneous magnetic field is produced during the interaction of ultra-short and ultra-intense laser with solids. It influences greatly the plasma wake -field acceleration, energy absorption, energy transport, the dynamics behaviors of electrons and ions, expansion of plasma, etc. People have studied the spontaneous magnetic field from theoretical simulation and experiment after J.A.Stamper measured the spontaneous magnetic field during the interaction of laser plasma in 1997.First, the ICF and the fast ignition are introduced simply. Secondly the basic concepts and theories for laser-plasma interaction are expatiated, then the recent research status, the generation mechanisms of spontaneous magnetic field during the interaction of laser-plasma are described in detail. Finally the introduction is focused on the experiment setup and results of spontaneous magnetic field on 20TW laser facility in China Academy of Engineering Physics Key Laboratory. In this thesis, the spontaneous magnetic field is deduced by the fine structure spectrum of 2(0 harmonics of the interaction of the ultra-short and ultra-intense laser with solid. Using the OMA optical multi-channel spectrometry , CCD(1152×1242) camera detect equipment and achromatic aberration camera lens for spatial distinguishing, we carried out the experiments to measure the one- dimension fine structure spectrum of 2(0 harmonics,and then investigated primarily the measurement system of scattering light. In the experiment, the pin-hole camera and CCD camera were employed to give the diameter of x-ray laser spot about 35 um , the laser energy about 530mJ,and the laser intensity on the target about 5×1017W/cm2. Especially, we have observed the 2(0 spectrum with satellite structure which was in agreement with PIC simulation of Zheng Jian. Additionally,according to the theory formula, the spontaneous magnetic field in the interaction of laser with the solids was up to MG ,which was also consistent well with the results of M. Borghesi and the thesis of Li Yutong for doctor degree。Dealing with spectrum in the spatial direction, we found that the spontaneous magnetic field was not uniform, but more intense in the circumference than in the central. That was also to say that the magnetic field was ring-shape distribution in the one-dimension space. On the other hand, what we have obtained also proved partly the theory of ring-shape magnetic field produced in the process of hot electrons escaping from the plasma.